Another fortuitous result of the collision of the Mars-sized planet with the Earth
is the presence of the Earth's large and heavy metallic core. In fact, the Earth has the
highest density of any of the planets in our Solar System. This large nickel-iron core is
responsible for our large magnetic field. This magnetic field produces the Van-Allen
radiation shield, which protects the Earth from radiation bombardment. If this shield were
not present, life would not be possible on the Earth. The only other rocky planet to have
any substantial magnetic field is Mercury - but its field strength is 100 times less than the Earth's.
The magnetic field of Mars is at least 1,000 times less than that of the
Earth. Even Venus, our sister planet, has no magnetic field. The Van-Allen radiation shield is a
design unique to the Earth.